Myenteric neuron numbers are maintained in aging mouse distal colon

Area of Science:

• Neuroscience
• Gastroenterology
• Aging Research

Background:

• Age-associated neuronal loss is known in various species.
• Cholinergic neurons are sometimes vulnerable, while nitrergic neurons are spared.
• Mouse enteric nervous system aging and specific neuron loss remain understudied.

Purpose of the Study:

• Investigate age-related changes in total neurons and specific subpopulations in the mouse distal colon.
• Quantify changes in myenteric neuron numbers and nerve fiber density during aging.
• Identify potential neurodegenerative alterations in aging mouse enteric nervous system.

Main Methods:

• Used wholemount preparations from mice aged 3–25 months.
• Double immunolabeling with HuC/D (total neurons), calbindin (CB), and neuronal nitric oxide synthase (nNOS).
• Confocal microscopy with new unbiased counting methods and corrections for gut dimension changes.

Main Results:

• No significant change in total or subpopulation myenteric neuron numbers with age.
• Decreased myenteric neuron density due to gut growth (3–12 months).
• Increased nNOS-immunoreactive nerve fiber density up to 18–19 months; observed neuronal process swelling.

Conclusions:

• Aging does not lead to myenteric neuron loss in the mouse distal colon within the studied age range.
• Neurodegenerative changes, including process swelling, occur with aging.
• These age-related changes may affect overall neuronal function in the enteric nervous system.